You'll be fine. I rode the exact same tires (28s) on my Cross Check, and still do on my commuter. I ride over the bridges in THP and GBP and have never had issues. The long boardwalk in GBP is in good shape for the most part. It'll rattle ya but it won't hurt your tires.
I now ride over them on 25s now without issue.
Don't worry about it. Just watch for the big splintering pieces.